The present invention relates to a pneumatically controlled respiration device in which the breathing gas, taken from a pressure-gas supply source through an injector and volumetrically metered in a pressure-regulating valve, is supplied, in the inspiration phase, to the user and discharged, in the expiration phase, through an exhaling valve.
A known pneumatically controlled respiration device comprises a combined pressure-regulating and control mechanism. This device includes a pressure chamber provided with an automatic inlet valve which, during the inspiration phase, admits pressure gas having a pressure corresponding to that in the lungs of the patient. In addition, the pressure chamber is provided with a controllable discharge mechanism. A final-control element is moved, during the inspiration phase, to close the inlet valve and, during the expiration phase, to open the same. The inhaling stroke is adjusted through an elastic tension member effective over the entire motion range of the final-control element, and through an additional elastic tension member which is effective only within the final step of this motion range.
The length of the expiration period is adjusted independently of the inspiration phase by means of the controllable discharge mechanism of the pressure chamber, by varying the cross-section of the discharge area.
The disadvantage of this device is the necessity of adjusting both the inspiration and the expiration time separately. This requires a great deal of skill, and a direct adjustment of the respiration frequency and of the respiration time ratio between the inspiration and expiration times is not possible (German Pat. No. 1,137,834).
In another known automatic respiration device, the flow of a breathing gas, supplied under the pressure of a gas source, is controlled by means of a control valve to which the breathing gas is delivered and which, in turn, is controlled by a controller switching in response to a certain inspiration volume and, thereby, closing the control valve, and reopening the same after a certain period of time of expiration. The controller is controlled, as a function of the passage of a certain gas volume, by a volume-control chamber mounted in parallel with a flow meter and releases a control impulse to close the control valve. The control valve is opened through a bellows as soon as the expiration phase is terminated and, up to this time, it is closed. The duration of the expiration phase may be varied by adjusting a discharge valve connected to the bellows.
This pneumatic device controls the inspiration phase in accordance with the inspiration volume and the expiration phase in time. The adjustment is complicated. Neither the respiration frequency nor the respiration time ratio can be adjusted directly (German Pat. No. 1,126,566).
Another known respiration device permits the release of the individual breathing phases, interfering in time with each other, both by the patient himself and by the device. The minimum time of the respective breathing phase, applied to the device as an input value or adjusted therein, causes a switching into the following breathing phase only upon expiration of the predetermined period of time, without a reversal effected by the spontaneous breathing of the patient. The automatic switching or release is effected by means of a relay circuit, and the reversal is effected through breathing by means of a control storage, in a well known manner.
In this device, the adjusted breathing phase is automatically switched over by electronic component parts requiring, aside from the necessary pressure-gas connection, a supply of electric energy. Electronic controls involve a complicated design and construction which, upon a failure, require a replacement of complete blocks (German Pat. No. 1,048,391).
It is common to all pneumatic systems that, for a controlled respiration, they do not permit a directly reproducible adjustment of the respiration frequency and the respiration time ratio. These values depend, inter alia, on the expiration phase. A certain experience is needed for an adjustment resulting in the desired frequency and the correct respiration time ratio with the right respiration volume.